Real-time imaging benefits prostate cancer treatment

Brachytherapy offers a nonsurgical treatment alternative for patients diagnosed with localized low-risk prostate cancer. For this treatment, small pellets — known as seeds — are implanted in the prostate where they emit radiation, destroying cancer cells within a few millimeters. The technique means that clinicians don’t have to surgically remove the prostate, thus minimizing the risk of impotence and certain other long-term side effects.

Earlier this year, radiation oncologists and urologists from Thomas Jefferson University’s Kimmel Cancer Center in Philadelphia began using a new system designed for implanting seeds in prostate cancer patients as well as for treatment planning and imaging.

Made by Nucletron BV of Veenendaal, the Netherlands, the system — the Spot Pro (Sonographic Planning of Oncology Treatments) — offers imaging-based implantation of seeds for brachytherapy, with three-dimensional needle guidance and real-time dosimetry updates. The system’s live imaging and live seed updates (with seed localization in a three-dimensional volume) enable physicians to build and adjust a treatment plan in real time, matching it to the position, location and condition of the prostate on the day of the procedure. Instant dose calculation allows optimization of needle placement and dose distribution, again, during the procedure.

Finally, because it is automated — gathering information and sending it to a computer for processing — the system provides for the most efficient configuration of the seeds during implantation. The physicians chose the Nucletron system, which was approved recently by the FDA, because it offers the greatest versatility for intraoperative treatment planning, said Dr. Richard K. Valicenti, an associate professor of radiation oncology at Jefferson Medical College. “We also liked the automated component of the seed placement capability.”

Until recently, they used the system only for treatment planning and imaging. For the former, its real-time capabilities have contributed to significant improvements in the precision of the procedure. With the previous approach, they would acquire a rough estimate of the size of the prostate gland several weeks before the procedure, using either MRI or CT. From this, they could determine the number of seeds they needed to order. When the patient returned, they would manually perform a volumetric measurement of the prostate and its relation to the rectum, bladder and urethra, and then put together a detailed plan for the procedure — including the position and the dosage.

The procedure took place still later. The concern always was whether the information obtained in an outpatient setting still would apply in the operating room, because the position, location and condition of the prostate might have changed. The real-time planning afforded by the recently acquired system assures that the information is up to date and more accurate. Furthermore, it allows the clinicians to adjust the dosage and other parameters during the procedure.

The system offers improved imaging as well. It obtains volumetric measurements by rotating the ultrasound probe rather than stepping along the axis of the probe — resulting in potentially less mobility of the prostate and greater stability, Valicenti explained. This approach provides for minimum disturbance of the prostate and, in addition, reduces the amount of time needed to perform imaging. Also, the system offers multiplanar imaging, providing a better understanding of the anatomical boundaries of the prostate gland.

The physicians have performed several dozen procedures with the system since April and were planning to implement it for seed implantation in late October. The standard approach had been to distribute the seeds evenly, typically with tight spacing of 5 mm to 1 cm. The robotic feature of the new system provides for greater variation in distribution, however. Thus, they can achieve more effective coverage of the region of interest.